I have many types of game-object that are related together is some ways.
All relations is implemented by Map<K1,K2>
.
#include <vector>
using namespace std;
template<class K1,class K2> class Map{ //N:N relation
public: std::vector<K2*> getK2(K1* k1){/* some code */return std::vector<K2*>();}
public: std::vector<K1*> getK1(K2* k2){/* some code */return std::vector<K1*>();}
//... various function ...
};
Here is the hub class GameRelation
that facilitates all relation query :-
(just an example, no need to pay attention to all detail)
class Human{}; class House{}; class Dog{};
class GameRelation{
public:
#define RELATION(A,B,EnumName) Map<A,B> Map##EnumName; \
enum EnumName##Enum{EnumName}; \
std::vector<B*> getAllRight(EnumName##Enum e,A* a){ \
return Map##EnumName.getK2(a); \
}
//... various function ...
RELATION(Human,House,Own)
//I can insert any relation that I want
};
The above macro expands into something like :-
Map<Human,House> MapOwn;
enum OwnEnum{Own};
std::vector<House*> getAllRight(OwnEnum e,Human* a){
return MapOwn.getK2(a);
}
Here is how it can be used (full demo):-
int main() {
GameRelation gameRelation;
std::vector<House*> houses=gameRelation.getAllRight(GameRelation::Own,new Human());
//get all "House" that is "Own" by a "Human"
return 0;
}
After some testing, it works good. Everyone is happy with the magical result.
However, my conscious tell me that it is a hack.
It is also a little bad for content-assist (e.g. intellisense) and automatic refactoring.
I also need the awesome hacking X-MACRO if I want to move their implementation to .cpp
.
Question:
struct GameRelation{
template <typename A, typename B>
struct Relation {
std::vector<B*> getAllRight(A* a) {
return map.getK2(a);
}
private:
Map<A, B> map;
};
Relation<Human, House> own;
};
int main() {
GameRelation gameRelation;
std::vector<House*> houses = gameRelation.own.getAllRight(new Human());
}